bad engine knock! PLEASE HELP!!!

what's up guys I own a 2005 chevy 2500 reg cab 6.0l with a 7"BDS ntbd. need some help here I've been looking on other forums trying to figure out what my loud obnoxious engine knocking is .
so I get home on Sunday from work go to bed. wake up Monday morning start my truck up and sounds like a freaking hammer hitting . my oil is good no metal in it. the lubricity is good I don't even know if that's a word but yeah. also I was reading about flex plates bending . I'm pretty sure it's not that. sound like passenger side lower area. checked for broken exhaust studs none are missing ., I'm at a stand still . just weird how this happened over night. . I don't know if it's a bad intake manifold gasket . but yet again I am not loosing coolant. also I was wondering if it could be a injector ?? making piston slap. or bad knock sensor. have the timing off . it's bad enough that it vibrates my whole truck.

haven't done anything to stress the motor out. she's my only ride and go about a mile and back ever day for work . try not to be too lead footed . gas is $$.
i checked coolant level and it was perfect and and normal height

ok I will pull injector . how would I know if injector is not working properly? hold a peice of white paper under it ?

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i have also read about the starter not fully engaging back complelty . to make a nasty noise of which I am hearing . I guess the bendix starters start to take a crap over a 100k which seems about right to what I hear .

if you have a fuel pressure gauge,that will determine leaking injector,i.e.quick drop in pressure,i agree with posts above,also while each spark plug is out,start it,this way also you can isolate to a specific cylinder,be quick about it so you dont harm cat.with unburned fuel

ok I will pull injector . how would I know if injector is not working properly? hold a peice of white paper under it ?

- - - Updated - - -

i have also read about the starter not fully engaging back complelty . to make a nasty noise of which I am hearing . I guess the bendix starters start to take a crap over a 100k which seems about right to what I hear .

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starter noise don't sound like pistons . these engines start very fast and I have yet to see starter failures of the drive/gears etc. usually the solenoids fail [no crank]

po300 is a pita.go to dealership and have a crankshaft relearn procedure done,only way i know of to get rid of that one,might not be out of the woods yet,so might have to wait on next code to appear,i.e. a hard code